For years, the key to weight loss has been obvious and simple: Eat less and move around more. Run 12 miles each day while licking a carrot and the pounds just melt away.

Kidding! Everyone on the internet knows that you can lose weight fast with This One Simple Trick, or This One Weird Trick. It's either a diet so rich in fiber you might as well eat a plank of particleboard, or it's a magic pill that makes the pounds fall off. Yes, a team of Actual Doctors (OK, podiatrists, but still doctors) have discovered a special substance called gullibilium. It increases your metabolism so high the food actually disappears on your fork before you eat it.

Act now and the second bottle is free! Money back if you don't have the BMI of a praying mantis by noon tomorrow! The pounds slide right off. And then the disclaimer: Use only in the tub or over a tarp because it's disgusting!

Nonsense, all of it. Oh, some pills might work; in the old days, they'd sell you pills that amped you up so high you lost weight because your hand shook so bad you couldn't fork the food into your face. But nowadays if you click on a link that takes you to a site that sells skinny pills, it's hogwash. You'd be better off washing a hog, because that burns energy.

You know this. You're smart. But be honest, what's your reaction to this:

A new study says taking a hot bath burns as many calories as 30 minutes of walking.

"Please, oh, please, be true" is what you're thinking. Because yesterday there was a box of doughnuts in the office. You didn't have an entire doughnut; that would be shameful. You had half. Later you went back to get the other half, thinking: I'm burning off the first half walking to get the second half. I'll put in an extra 10 minutes on the treadmill. Note to self: Buy a treadmill.

What if you could negate those calories by spending half an hour in the tub shaping the bubbles into a beard for your rubber duck?

It appears to be true. Science says so. We're not just talking a scientific study by doctors, but English doctors with impressive accents.

The study comes from Loughborough University, where researchers set out to study "the effect of passive heating on heat shock protein 70 and interleukin-6." I know, I know, I've been wondering about that myself. And here are the results of their study:

Cycling burned more calories than sitting in the tub, because: duh. But a hot bath burned as many calories as a half-hour walk — 140, to be exact.

How does this work? Now, I'm just an old country columnist without any fancy scientific schooling, but I'm thinking of an ice cube in a sauna. But there are probably limits, and drawbacks — say, six hours in a hot bath counteracts a bowl of ice cream but makes you look all-over pruney.

Might be worth it anyway, just to see what people say.

"Hey, how you doing? You've lost weight! Have you been working out, and also aging at an alarming rate? You look thinner but horribly wrinkled."

"Nope, went on the Bathtub Diet. Also doin' Atkins and Paleo. Soon you'll be able to mail me with a first-class stamp."

The study wasn't some vast clinical experiment; only 12 men were observed. But Loughborough boffins say they'll continue to investigate the healing powers of heat as well as its caloric impact.

In the meantime, don't give up walking quite yet. And don't think "I'm busy, who has time for a half-hour bath? I'll just do jumping jacks in the shower." If you must do that, at least wear sensible shoes. You could slip.

james.lileks@startribune.com • 612-673-7858 • Twitter: @Lileks • facebook.com/james.lileks